In Praise of an SPL meter...

[Bobbsy]

We've had a few threads in here complaining about venues that use SPL meters to cut off power to the sound system if certain levels are exceeded. I can see that this could be very annoying, though I also understand the risks of high sound levels.

 

However, for the last few days I've been working in a very well equipped venue that actually had a constant display of SPL available at the mixing desk. I found this both interesting and useful.

 

Over a few days we did the same show quite a few times with two and sometimes three runs per day. I've always tried to be aware of the physical and psychological effects that cause "fader creep" over a run and try to make myself stick to certain pre-set levels. However, it was fascinating to see the absolute levels displayed. After several shows in quick succession, had I depended on my ears alone, I would almost certainly have increased the levels...or, put another way, the show started to sound quieter to me.

 

Clearly, as we often say, your ears are your most valuable tool in mixing. However, it was very interesting to see in passing how pyschoacoustics can fool you. Mixing with an SPL display in front of me was an instructive experience.

 

I toss this out for discussion!

 

Bob

[mervaka]

I carry one with me, but in smaller venues turning the overall level down is easier said than done, what with drum kits to compete with! (and the arrogant artists who insist on having their amps cranked to 11 without a hotplate)

[The Boogie Man]

Slightly ot, but was this a built in unit, or an add on that is availble to buy somewhere?

[Kevin Ross]

I once saw a venue with a very large LED display with the sound pressure in DB displayed throughout the gig. What I tend to do is hook up my laptop to the main L+R outputs of my desk and run either a piece of SA software with a level built in. I know it’s not calibrated but it gives me an idea of if I’m creeping the levels up. I also carry a DB meter that I check during soundcheck and at the start of the show but its too hard at a glance hence the laptop

[Bobbsy]

Slightly ot, but was this a built in unit, or an add on that is availble to buy somewhere?

 

It was an add-on mounted on top of the dog house at one end of the console. Because of the way it was mounted, I couldn't see any manufacturer name but it was a nice big, simple LED display. Indeed, I wonder if it was just a standard LED box somehow remoted from a more conventional SPL meter. I'll have to ask the venue manager next time in in there (assuming I get asked back!)

 

I also carry a basic SPL meter when I take in my own kit but tend to use it mostly at set up...the display (at least on my unit) wouldn't be the easiest to read in the dark during a show.

 

In this case, it was a dance show (ballet) and the absolute levels were kept pretty low. What I found more interesting was the absolute proof of how easy it is (through a mix of listening fatique and over familiarity) for your perceptions of the sound levels to be wrong and to let your levels creep up...even if you're aware of the problem and try to avoid it.

 

Bob

[Lamplighter]

Bob

I find this most interesting, having suffered from the 'creep' problem in a couple of venues over the last few years. It would be useful to know where the mic was located, what weighting and response speed were applied, and also if the readings felt 'real' or just a number.

Brian

[Rob_Beech]

What a great idea. On that should be implemented much more often IMO.

 

If this was an off the shelf unit then I'd certainly like to know. However it shouldn't be too difficult to make such an item. Using a normal digital SPL meter you could "modify" this so that the physical output to its own screen output to the larger screen (providing they are the same type which it appears they are). The only thing would be having enough oomph to "drive" the larger screen so some other cleverness maybe required. Overall I can't see how it would be overly complicated.

 

 

I currently use a spare Behringer DEQ2496 and their RTA mic at gigs to get an SPL reading. It would be nice if the display could alter to provide 96 in big numbers rather than a moving bar and a tiny number next to it but it can still be seen. Maybe if Uli's reading we might see that in future.

[Bobbsy]

I wasn't able to get any details while doing this show. Basically the theatre in question normally has a Head of Sound and a full time assistant so there's not a huge amount of freelance work there. However, the Head of Sound was committed to doing a "Shakespeare in the Park" show and had to be out...and the assistant who was supposed to work the show I did had a fall and was in bed at home. This meant that I got a very quick handover and was left to my own devices with nobody there I could ask detailed questions of.

 

Once the HoS is back (after the Shakespeare festival) I'll see if I can find out more about their system.

 

In the meantime, at a guess it was "A" weighted since the readings seemed to pretty closely correlate to what I was hearing across the frequency range. The response speed was pretty quick...certainly there was no noticeable lag as the music I was playing in swelled to crescendos--but there was just enough delay on the the decay to make is useful rather than a constant flicker.

 

One question I can answer is Brian's: yup, the information it provided did feel "real". The indicated readings matched very nicely with rises and falls in SPL that I was hearing...it just "kept me honest" where, after 5 shows in 2 days I would likely have been accidentally using somewhat higher levels by the end.

 

I'll post again when/if I can get some answers!

 

Bob

[saturnx21]

Was it something like this: Linky

 

Seems very expensive though! <_<

[mac.calder]

We keep a small "Radio Shack" analogue SPL meter in our rack drawer to prevent fader creep.

 

We have a fairly strict "108 at the back wall" policy enforced by the venue, although nothing as draconian as power cutting occurs if this level is breached, they do send someone in with a decent quality SPL meter about once a month, and nasty emails get sent if their meter crosses the 108 threshold.

 

Whilst I can see the value in a big LCD display screaming out the values, a decent analogue meter with a decent range division is almost as good. Ours, we set at 110, which has 110dB at the upright position, and 105 at 9 o'clock. So if the needle moves, pull back. Works really well. Since its purchase, we have not had a single noise related non-compliance.

[djmatthill]

Here we have a very afforable meter

 

http://www.action-electronics.com/dbmeter.htm

 

<_<

[smalljoshua]

Here we have a very afforable meter

 

http://www.action-electronics.com/dbmeter.htm

 

<_<

On that note...

 

Maplin have a digital meter for £29 Linky

 

Josh

[Rob_Beech]

On that note nothing at all. The thread isn't about listing regular meters. It's about easy to read displays either as a stand alone unit, or perhaps as an add on to an existing unit.

[Bobbsy]

Thanks Rob. Most of us here have probably used things like the Maplins and RS meters shown. This thread was about something different that I've not encountered before.

 

The closest thing is the unit that saturnx21 posted the link to, but this one was simpler, without the bar-graph meter or (as far as I know) the colour change at pre-set levels. It was literally just a box with an LED numeric display (which is one of the reasons I wonder it it might have been a remote display of a more conventional meter.

 

Anyhow, I've left a message for the guy who would know and will post more if/when I hear back.

 

Bob

[Mr.Si]

Bobbsy,

 

The two main units I've come across in my time being a freelance noiseboy in the odd social club and my day job of acoustic consultancy are on

 

this website

 

Formula Sound's "Sentry 73" (here)

and

Castle's "Electronic Orange" (here)

 

The Sentry 73 says it has facility for a slave display. I am not sure if the Electronic Orange does.

 

Something I've come across, which is bad (though I understand why they do it), is that the AVC units which are set up in a power cut-off mode will control certain sockets only. Now the owners of some venues will tell people not to plug in to those sockets when in fact they should be make sure that they do use them.

 

It's the "do you want a problem with the council and your neighbours, or do you want un-happy punters who want the sound louder" issue.

 

I'm not sure if they have these units in the land of Oz, but I'd hazard a guess that Castle and Formula Sound are both international companies, so it wouldn't surprise me if they were.

 

My 2p, hope it was useful for the piggy bank.

 

 

Si